大约75%的儿童因1q21.1 染色体微缺失发育滞后,体现在会影响运动技能的发展,如坐着,站着,散步。智力残疾和学习问题等相关基因变化，但这通常是相对温和的。面部独特的特征也可以与1q21.1 染色体微缺失相关。变化通常是微妙的,包括前额突出,一个大的圆形的鼻尖,长鼻子和上唇之间的空间相对较高,拱形屋顶般的嘴。其他常见的体征和症状也和1q21.1 微小缺失有关联，其中包括头小畸型,身材矮小,白内障等问题。 1q21.1 微小缺失影响较少,就是心脏缺陷,生殖器或泌尿系统畸形,骨骼异常(特别是手和脚),和听力损失。
1q21.1 微小缺失没有人可以用任何知识的物理或精神上面描述的特性。在部分些个体中,微小缺失是当他们接受基因检测发现的,因为他们有与染色体的相对不同变化。未知原因会使1q21.1 微小缺失导致一些人认知和生理发生变化,甚至在同一个家庭很少或根本没有健康问题。
大多数人用1q21.1 微小缺失比较，失踪约135万DNA序列构建块(碱基对),也写成1.35 megabases(Mb),q21.1地区的染色体1。然而,精确缺失区域的大小是不同的。这缺失影响染色体1在每个单元的两个副本。个体体征和症状可以从1结果q21.1 微小缺失可能相关的几个基因在这一地区的损失。研究人员正在努力确定哪些基因缺失导致相关的特定功能缺失。因为一些人用1q21.1 微小缺失没有明显的相关功能,额外的遗传或环境因素被认为是参与体征和症状的发展。
研究人员有时指1q21.1 微小缺失作为远端复发1.35 mb缺失来区分它的基因改变引起thrombocytopenia-absent半径(TAR)综合症。焦油综合症缺失的结果不同,小的DNA片段染色体1q21.1地区附近的地方1.35 mb缺失的发生。相关的染色体改变焦油综合症通常被称为200 kb的缺失。
至少一半的情况下,个人1q21.1 微小缺失继承父母的染色体变化。 一般来说,家长携带1q21.1 微小缺失有温和的体征和症状比他们的孩子继承这缺失,即使缺失是相同的大小的。大约四分之一的家长没有关联这特性的。
1q21.1 微小缺失也可以发生在那些父母不携带染色体改变。 在这种情况下,缺失最常作为随机事件发生在生殖细胞的形成(卵子或精子)在父母或早期胚胎发育。
What is 1q21.1 microdeletion?
1q21.1 microdeletion is a chromosomal change in which a small piece of chromosome 1 is deleted in each cell. The deletion occurs on the long (q) arm of the chromosome in a region designated q21.1. This chromosomal change increases the risk of delayed development, intellectual disability, physical abnormalities, and neurological and psychiatric problems. However, some people with a 1q21.1 microdeletion do not appear to have any associated features.
About 75 percent of all children with a 1q21.1 microdeletion have delayed development, particularly affecting the development of motor skills such as sitting, standing, and walking. The intellectual disability and learning problems associated with this genetic change are usually mild.
Distinctive facial features can also be associated with 1q21.1 microdeletions. The changes are usually subtle and can include a prominent forehead; a large, rounded nasal tip; a long space between the nose and upper lip (philtrum); and a high, arched roof of the mouth (palate). Other common signs and symptoms of 1q21.1 microdeletions include an unusually small head (microcephaly), short stature, and eye problems such as clouding of the lenses (cataracts). Less frequently, 1q21.1 microdeletions are associated with heart defects, abnormalities of the genitalia or urinary system, bone abnormalities (particularly in the hands and feet), and hearing loss.
Neurological problems that have been reported in people with a 1q21.1 microdeletion include seizures and weak muscle tone (hypotonia). Psychiatric or behavioral problems affect a small percentage of people with this genetic change. These include developmental conditions called autism spectrum disorders that affect communication and social interaction, attention deficit hyperactivity disorder (ADHD), and sleep disturbances. Studies suggest that deletions of genetic material from the 1q21.1 region may also be risk factors for schizophrenia.
Some people with a 1q21.1 microdeletion do not have any of the intellectual, physical, or psychiatric features described above. In these individuals, the microdeletion is often detected when they undergo genetic testing because they have a relative with the chromosomal change. It is unknown why 1q21.1 microdeletions cause cognitive and physical changes in some individuals but few or no health problems in others, even within the same family.
How common is 1q21.1 microdeletion?
1q21.1 microdeletion is a rare chromosomal change; only a few dozen individuals with this deletion have been reported in the medical literature.
What are the genetic changes related to 1q21.1 microdeletion?
Most people with a 1q21.1 microdeletion are missing a sequence of about 1.35 million DNA building blocks (base pairs), also written as 1.35 megabases (Mb), in the q21.1 region of chromosome 1. However, the exact size of the deleted region varies. This deletion affects one of the two copies of chromosome 1 in each cell.
The signs and symptoms that can result from a 1q21.1 microdeletion are probably related to the loss of several genes in this region. Researchers are working to determine which missing genes contribute to the specific features associated with the deletion. Because some people with a 1q21.1 microdeletion have no obvious related features, additional genetic or environmental factors are thought to be involved in the development of signs and symptoms.
Researchers sometimes refer to 1q21.1 microdeletion as the recurrent distal 1.35-Mb deletion to distinguish it from the genetic change that causes thrombocytopenia-absent radius (TAR) syndrome. TAR syndrome results from the deletion of a different, smaller DNA segment in the chromosome 1q21.1 region near the area where the 1.35-Mb deletion occurs. The chromosomal change related to TAR syndrome is often called the 200-kb deletion.
Read more about chromosome 1.
See a list of genes associated with 1q21.1 microdeletion.
Read more about thrombocytopenia-absent radius syndrome.
Can 1q21.1 microdeletion be inherited?
1q21.1 microdeletion is inherited in an autosomal dominant pattern, which means that missing genetic material from one of the two copies of chromosome 1 in each cell is sufficient to increase the risk of delayed development, intellectual disability, and other signs and symptoms.
In at least half of cases, individuals with a 1q21.1 microdeletion inherit the chromosomal change from a parent. In general, parents who carry a 1q21.1 microdeletion have milder signs and symptoms than their children who inherit the deletion, even though the deletion is the same size. About one-quarter of these parents have no associated features.
A 1q21.1 microdeletion can also occur in people whose parents do not carry the chromosomal change. In this situation, the deletion occurs most often as a random event during the formation of reproductive cells (eggs or sperm) in a parent or in early embryonic development.
Where can I find information about diagnosis or management of 1q21.1 microdeletion?
These resources address the diagnosis or management of 1q21.1 microdeletion a